Heavy hydrocarbon removal systems and methods

ABSTRACT

Apparatuses and systems for removing heavy hydrocarbons from a solvent stream are disclosed herein. The apparatuses extract heavy hydrocarbons into light hydrocarbons and provide a solvent stream having the heavy hydrocarbons removed. Two water washing steps are used to remove residual solvent from the heavy hydrocarbon solution in light hydrocarbons. In some embodiments, the second water wash is used for processing subsequent batches of the solvent stream. The heavy hydrocarbons and solvent can be recovered and processed further. Methods for removing heavy hydrocarbons from a solvent stream are also disclosed herein.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. provisional patent application61/121,153, filed Dec. 9, 2008, which is incorporated by referenceherein in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not applicable.

BACKGROUND

Heavy hydrocarbons such as bitumen, kerogen, GILSONITE® (trademarkedterm of the mineral uintahite) and tars are high molecular weighthydrocarbons frequently encountered in the petroleum industry. Theseheavy hydrocarbons range from thick viscous liquids to solids at ambienttemperatures and are generally difficult to recover in useful form. Forexample, heavy hydrocarbon crude oils and natural bitumens are difficultto handle because their low gravities and high viscosities retard theirability to flow within a reservoir or refinery stream. Furthermore,heavy hydrocarbons can build up over time in various processing streamsat a refinery, fouling system output or requiring costly processdowntime.

Although heavy hydrocarbons are problematic in refinery processing ofpetrochemicals, there are a number of applications in which heavyhydrocarbons are useful. Heavy hydrocarbons have been used, for example,as asphalt and tar compositions, including those used for paving roadsand roofing or waterproofing applications. Heavy hydrocarbons are also afeedstock for conversion into lighter hydrocarbons, such as olefins andgasoline. Conversion of heavy hydrocarbons into lighter hydrocarbons istypically accomplished by thermal cracking and hydrogenolysis processes,for example.

In view of the foregoing, apparatuses and methods to easily separateheavy hydrocarbons from a solvent stream at a refinery would be ofconsiderable benefit. Such apparatuses and methods would allow moreefficient operation of refinery process streams and also provide theheavy hydrocarbons in useful form for further processing.

SUMMARY

In various embodiments, apparatuses for removing heavy hydrocarbons froma solvent stream are disclosed. The apparatuses include a firstextractive unit, a second extractive unit and a light hydrocarbon inputline coupled to the first extractive unit. The first extractive unitincludes a first water input line, a solvent stream output line, and afirst heavy hydrocarbon output line. The first heavy hydrocarbon outputline is coupled to the second extractive unit. The second extractiveunit includes a second water input line, a second water output line, anda second heavy hydrocarbon output line. The second water output lineadjoins the first water input line.

In other various embodiments, apparatuses for removing heavyhydrocarbons from a solvent stream include a first extractive unit, asecond extractive unit and a light hydrocarbon input line coupled to thefirst extractive unit. The first extractive unit includes a first waterinput line, a solvent stream output line, and a first heavy hydrocarbonoutput line. The first heavy hydrocarbon output line is coupled to thesecond extractive unit. The first water input line is supplied bycondensed stripping steam. The second extractive unit includes a secondwater input line, a second water output line, and a second heavyhydrocarbon output line.

In other various embodiments, methods for removing heavy hydrocarbonsfrom a solvent stream are disclosed. The methods include a) providing afirst batch of a mixture containing heavy hydrocarbons dissolved in atleast one solvent, b) extracting the first batch of the mixture with alight hydrocarbon wash, c) washing the first batch of the mixture with afirst water wash to produce a solvent stream depleted in heavyhydrocarbons and a heavy hydrocarbon stream dissolved in lighthydrocarbons, d) removing the solvent stream depleted in heavyhydrocarbons, e) washing the heavy hydrocarbon stream dissolved in lighthydrocarbons with a second water wash, f) removing the second waterwash, and g) isolating an output stream containing heavy hydrocarbonsdissolved in light hydrocarbons.

The foregoing has outlined rather broadly the features of the presentdisclosure in order that the detailed description that follows may bebetter understood. Additional features and advantages of the disclosurewill be described hereinafter, which form the subject of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and theadvantages thereof, reference is now made to the following descriptionsto be taken in conjunction with the accompanying drawings describingspecific embodiments of the disclosure, wherein:

FIG. 1 shows an illustrative heavy hydrocarbon removal system; and

FIG. 2 shows an illustrative coupling of a heavy hydrocarbon removalsystem to a solvent regeneration system.

DETAILED DESCRIPTION

In the following description, certain details are set forth such asspecific quantities, sizes, etc. so as to provide a thoroughunderstanding of the present embodiments disclosed herein. However, itwill be evident to those of ordinary skill in the art that the presentdisclosure may be practiced without such specific details. In manycases, details concerning such considerations and the like have beenomitted inasmuch as such details are not necessary to obtain a completeunderstanding of the present disclosure and are within the skills ofpersons of ordinary skill in the relevant art.

Referring to the drawings in general, it will be understood that theillustrations are for the purpose of describing a particular embodimentof the disclosure and are not intended to be limiting thereto. Drawingsare not necessarily to scale.

While most of the terms used herein will be recognizable to those ofskill in the art, it should be understood, however, that when notexplicitly defined, terms should be interpreted as adopting a meaningpresently accepted by those of ordinary skill in the art. In cases wherethe construction of a term would render it meaningless or essentiallymeaningless, the definition should be taken from Webster's Dictionary,3rd Edition, 2009. Definitions and/or interpretations should not beincorporated from other patent applications, patents, or publications,related or not, unless specifically stated in this specification or ifthe incorporation is necessary for maintaining validity.

“Raffinate,” as used herein, refers to, for example, light hydrocarbons.

Heavy hydrocarbon buildup in refinery systems such as, for example,extractive distillation systems can be problematic, particularly whenthe systems have a closed-loop circulation. Oftentimes, heavyhydrocarbon buildup occurs gradually over time, for example, when theboiling point of the heavy hydrocarbons is close to the boiling point ofthe material being produced in the closed-loop system. In such cases,separation of heavy hydrocarbons by simple distillation can be difficultor is otherwise energy inefficient. When separation is difficult and,heavy hydrocarbons build up over time, performance of the refinerysystem can be fouled. In such cases where separation of heavyhydrocarbons is not easily accomplished, alternative separation methodsare often used to maintain production quality and optimal systemperformance. In the discussion that follows, an illustrative refineryprocess of extractive distillation is described. However, one ofordinary skill in the art will recognize that the apparatuses andmethods for removing heavy hydrocarbons described herein may be used forany of a number of refinery processes where it is desirable to removeheavy hydrocarbons. The apparatuses and methods discussed hereinbelowincorporate a light hydrocarbon extraction to remove heavy hydrocarbonsfrom a solvent stream in an extractive distillation process. Theapparatuses and methods are advantageous over existing apparatuses andmethods in that other than the heavy hydrocarbon output stream produced,there is a very low quantity of water and organic waste streams thathave to be dealt with in operating the apparatuses or practicing themethods.

In various embodiments, apparatuses for removing heavy hydrocarbons froma solvent stream are disclosed. The apparatuses include a firstextractive unit, a second extractive unit and a light hydrocarbon inputline coupled to the first extractive unit. The first extractive unitincludes a first water input line, a solvent stream output line, and afirst heavy hydrocarbon output line. The first heavy hydrocarbon outputline is coupled to the second extractive unit. The second extractiveunit includes a second water input line, a second water output line, anda second heavy hydrocarbon output line. The second water output lineadjoins the first water input line. The apparatuses allow batchwiseprocessing of a solvent stream containing heavy hydrocarbons. Theapparatuses can be operated continuously in certain embodiments.

In some embodiments, the apparatuses include detection sensors formonitoring the solvent stream and automatically activating theapparatuses when deemed necessary to remove heavy hydrocarbons from thesolvent stream. For example, a threshold concentration of heavyhydrocarbons may be reached in the solvent stream and trigger theoperation of the apparatuses. In some embodiments, the flow rate of thesolvent stream can dictate an event suggesting that heavy hydrocarbonremoval should be performed. For example, as heavy hydrocarbons build upin the solvent stream, the solvent stream viscosity may become too greatfor optimal system operation, and activation of the apparatuses based onviscosity of the solvent stream may take place. The apparatuses forremoving heavy hydrocarbons can also be triggered automatically bydetecting, for example, a concentration of heavy hydrocarbons in thesolvent stream above a certain allowable level. In some embodiments, theallowable level is about 1 wt. % heavy hydrocarbons, in others about 5wt. %, in others about 10 wt. %, in others about 20 wt. %, in othersabout 30 wt. %, in others about 40 wt. %, in others about 50 wt. %, andin still others greater than about 50 wt. %. Concentration detection ofheavy hydrocarbons may be accomplished, for example, by viscositymeasurement. One of ordinary skill in the art will recognize that theconcentration of heavy hydrocarbons in the solvent stream will at leastinitially depend on the concentration of heavy hydrocarbons in theoriginal petroleum feed upon which extractive distillation is performed.

In various embodiments of the apparatuses, the solvent stream comprisesa closed-loop solvent stream. As discussed hereinabove, a closed-loopsolvent stream is conducive to buildup of heavy hydrocarbons. In variousembodiments, the apparatuses further include a solvent regenerationsystem coupled to the solvent stream output line. For example, solventcan be removed from the solvent stream output line, regenerated with thesolvent regeneration system, and placed back into the extractivedistillation system Such solvent regeneration systems may include, forexample, processes and systems to remove water from the solvent beforeplacing it back into the extractive distillation system. In someembodiments, the solvent regeneration system is a two-stage vaporizationsystem.

In various embodiments, the apparatuses are coupled to an extractivedistillation system. In embodiments where the apparatus are coupled toan extractive distillation system, the extractive distillation may beused for extractive distillation of aromatic compounds. Aromaticcompounds may include benzene, toluene and xylenes, for example.

When a threshold concentration of heavy hydrocarbons is detected in theclosed-loop extractive distillation system, a controlled portion of thesolvent containing heavy hydrocarbons is automatically transferred andprocessed by the apparatuses for removing heavy hydrocarbons disclosedherein. FIG. 1 shows an illustrative heavy hydrocarbon removal system100. The heavy hydrocarbon removal system includes first extractive unit120 and second extractive unit 130. A solvent source 101 containingheavy hydrocarbons in a solvent is treated with a light hydrocarbon(LHC) feed from light hydrocarbon input line 102. The light hydrocarbonfeed dilutes the mixture of heavy hydrocarbons in the solvent. Mixing isaccomplished, for example, in solvent/LHC static mixer 103. Heavyhydrocarbons are extracted in the light hydrocarbons. A first water washis supplied from first water input line 104. Mixing of the water fromfirst water input line 104 with the solvent/LHC mixture of heavyhydrocarbons occurs in water/solvent/LHC static mixer 105. Theapparatuses also include two separators 106 and 107. The first stageseparator 106 accomplishes removal of the solvent from the bottom of theseparator as a water-containing phase. Removal of the water-based phaseoccurs through solvent stream output line 112. The solvent stream, whichnow depleted of heavy hydrocarbons, can be processed further forplacement back into the extractive distillation system. Alternately, thewater-containing phase containing dissolved solvent can be furtherprocessed for solvent recovery, water recirculation, disposal, or acombination thereof. The top phase remaining in first stage separator106 includes heavy hydrocarbons dissolved in a light hydrocarbonextract.

The top phase in the first stage separator 106 contains a small amountof dissolved or admixed solvent along with the heavy hydrocarbons in thelight hydrocarbon extract. For disposal or further processing of theheavy hydrocarbons, is advantageous to remove the remaining solvent fromthe heavy hydrocarbons dissolved in the light hydrocarbon extract.Following removal of the majority of the solvent in the water-containingphase of first stage separator 106, the heavy hydrocarbons dissolved inlight hydrocarbons are transferred from the first stage separator 106through first heavy hydrocarbon output line 113 and mixed with freshwater supplied from second water input line 108. Mixing of the heavyhydrocarbons in light hydrocarbons takes place in water/heavyhydrocarbon/LHC static mixer 109. The mixture is then transferred tosecond stage separator 107. The residual solvent in the heavyhydrocarbon/LHC phase is extracted into the second water wash andremoved as the bottom layer in second stage separator 107. The heavyhydrocarbon phase is separated as the top layer in second stageseparator 107 and removed as a heavy hydrocarbon output stream throughsecond heavy hydrocarbon output line 110. The heavy hydrocarbonsobtained through second heavy hydrocarbon output line 110 remaindissolved in a light hydrocarbon solution for further processing. Forexample, the light hydrocarbons can be removed during further processingor the heavy hydrocarbon output can be directly disposed of.

The water wash removed from the bottom of second stage separator 107contains primarily traces of solvent not separated from the heavyhydrocarbon/LHC mixture in the first stage separator 106. As such, thewater wash so obtained is suitable to be used as a wash for a secondtime for removing larger quantities of solvent. The apparatusesdescribed herein include a second water output line 111, whereby thewater wash removed from second stage separator 107 can be utilized as afirst water wash for a second batch of heavy hydrocarbons dissolved insolvent. Second water output line 111 adjoins first water input line104. Second water output line 111 allows the heavy hydrocarbonseparation apparatus 100 to operate as a closed-loop system. Theclosed-loop setup offered by second water output line 111 isadvantageous, since it allows continuous batchwise separation of heavyhydrocarbons from a solvent stream. Further, utilizing the second waterwash for a first water wash in subsequent extraction batches lowerswaste water disposal costs and mitigates other considerations commonlyassociated with wastewater.

In other various embodiments, apparatuses for removing heavyhydrocarbons from a solvent stream include a first extractive unit, asecond extractive unit and a light hydrocarbon input line coupled to thefirst extractive unit. The first extractive unit includes a first waterinput line, a solvent stream output line, and a first heavy hydrocarbonoutput line. The first heavy hydrocarbon output line is coupled to thesecond extractive unit. The first water input line is supplied bycondensed stripping steam. The second extractive unit includes a secondwater input line, a second water output line, and a second heavyhydrocarbon output line. In various embodiments of the apparatuses, thesolvent stream comprises a closed-loop solvent stream. In variousembodiments, the apparatuses further include a solvent regenerationsystem coupled to the solvent stream output line. In some embodiments,the solvent regeneration system is a two-stage vaporization system.

In some embodiments of the apparatuses, the condensed stripping steam isfrom aromatic extractive distillation process. In some embodiments ofthe apparatuses, the stripping steam is produced by a solventregeneration system.

An illustrative process for which heavy hydrocarbon removal isadvantageous is in aromatic extractive distillation. The aromaticextractive distillation process can be coupled to a heavy hydrocarbonremoval apparatus and a solvent regeneration system. FIG. 2 shows anillustrative coupling of a heavy hydrocarbon removal system to a solventregeneration system. Solvent reservoir 201 is connected an aromaticextractive distillation process. As the solvent in solvent reservoir 201becomes laden with heavy hydrocarbons, a portion of the solvent isreleased from solvent reservoir 201 into line 211 en route to heavyhydrocarbon removal system 204. An illustrative heavy hydrocarbonremoval system was previously described hereinabove and illustrated inFIG. 1. The solvent containing heavy hydrocarbons is treated with lighthydrocarbons from light hydrocarbon input line 202 and water from waterinput line 203. The mixture of heavy hydrocarbons, solvent, lighthydrocarbons and water is fed into heavy hydrocarbon removal system 204.For example, as discussed hereinabove, the mixture of heavyhydrocarbons, solvent, light hydrocarbons and water is passed into afirst extractive unit and then a second extractive unit to separatewater and solvent from heavy hydrocarbons and light hydrocarbons. Heavyhydrocarbons dissolved in light hydrocarbons are removed through heavyhydrocarbon output line 205. The residual water and solvent depleted ofheavy hydrocarbons are removed through line solvent stream output line206. The residual water and solvent arise from the first extractiveseparation of water and solvent from a light hydrocarbon solution ofheavy hydrocarbons.

In the embodiment shown in FIG. 2, the solvent stream depleted of heavyhydrocarbons is fed from solvent stream output line 206 into a two-stagevaporization system having first vaporization unit 207 and secondvaporization unit 208. From the first vaporization unit 207 and secondvaporization unit 208, the solvent is passed to a solvent regenerationsystem 209. The solvent regeneration system 209 generates strippingsteam in the course of regenerating the solvent. The stripping steam canbe condensed and used in a closed-loop for the water washes of the heavyhydrocarbon removal system (i.e., for water input line 203 above).Purified solvent is fed back to solvent reservoir 201 through line 212,which is thereafter fed back into the aromatic extractive distillationprocess.

Stripping steam generated from the solvent regeneration system 209 canbe condensed and used as at least the first water wash in the heavyhydrocarbon removal system 204. Coupling of the solvent regenerationprocess to the heavy hydrocarbon removal process provides anadvantageous operational benefit. Not only are heavy hydrocarbonsremoved from the solvent stream, but utilization of the stripping streamin the heavy hydrocarbon removal process minimizes water release aswastewater.

One of ordinary skill in the art will recognize that the heavyhydrocarbon removal system discussed above may be coupled to any of anumber of processing conditions wherein removal of heavy hydrocarbons isadvantageous, and the embodiment coupled to an aromatic extractivedistillation process presented hereinabove should be consideredillustrative. One of ordinary skill in the art will further recognizethat the apparatuses discussed hereinabove are advantageous in notgenerating excessive amounts of waste solvent, waste water or wasteheat. One of the only organic waste streams generated by the apparatusesis the LHC/heavy hydrocarbon stream. In some embodiments, even theLHC/heavy hydrocarbon stream can be further processed, for example, forblending into a liquid fuel system or by being transferred to anotherrefinery unit, for example, to crack the heavy hydrocarbons into moreuseful small organics.

In other various embodiments, methods for removing heavy hydrocarbonsfrom a solvent stream are disclosed. The methods include a) providing afirst batch of a mixture containing heavy hydrocarbons dissolved in atleast one solvent, b) extracting the first batch of the mixture with alight hydrocarbon wash, c) washing the first batch of the mixture with afirst water wash to produce a solvent stream depleted in heavyhydrocarbons and a heavy hydrocarbon stream dissolved in lighthydrocarbons, d) removing the solvent stream depleted in heavyhydrocarbons, e) washing the heavy hydrocarbon stream dissolved in lighthydrocarbons with a second water wash, f) removing the second waterwash, and g) isolating an output stream containing heavy hydrocarbonsdissolved in light hydrocarbons. In various embodiments, the methodsfurther include providing a second batch of a mixture containing heavyhydrocarbons and repeating the method steps. Accordingly, methods forremoving heavy hydrocarbons as herein disclosed can be conductedcontinuously.

In various embodiments of the methods, the solvent stream is aclosed-loop solvent stream. In various embodiments of the methods, thesolvent stream includes aromatic compounds. In various embodiments ofthe methods, the extracting step removes heavy aromatic compounds.

In various embodiments of the methods, the second water wash used towash the first batch of the mixture is subsequently transferred in aclosed-loop system such that the second water wash becomes the firstwater wash for a second batch of the mixture containing heavyhydrocarbons and at least one solvent. Such reuse of the second waterwash has been described in more detail hereinabove. In variousembodiments, the methods further include regenerating the at least onesolvent from the solvent stream depleted in heavy hydrocarbons. Theregenerating step includes using a solvent regeneration system. Thesolvent regeneration system regenerates solvent for re-introduction backinto the solvent stream. In various embodiments of the methods, thefirst water wash comprises condensed stripping steam produced by thesolvent regeneration system.

In various embodiments of the methods, a threshold concentration ofheavy hydrocarbons dissolved in the at least one solvent triggersoperation of the method. Various threshold parameters and methods ofsensing the threshold concentration have been considered hereinabove. Invarious embodiments, the methods further include transferring the heavyhydrocarbon stream dissolved in light hydrocarbons prior to the secondwashing step.

From the foregoing description, one of ordinary skill in the art caneasily ascertain the essential characteristics of this disclosure, andwithout departing from the spirit and scope thereof, can make variouschanges and modifications to adapt the disclosure to various usages andconditions. The embodiments described hereinabove are meant to beillustrative only and should not be taken as limiting of the scope ofthe disclosure, which is defined in the following claims.

1. An apparatus for removing heavy hydrocarbons from a solvent stream,said apparatus comprising: a first extractive unit and a secondextractive unit; wherein the first extractive unit comprises a firstwater input line, a solvent stream output line, and a first heavyhydrocarbon output line; wherein the first heavy hydrocarbon output lineis coupled to the second extractive unit; wherein the second extractiveunit comprises a second water input line, a second water output line,and a second heavy hydrocarbon output line; wherein the second wateroutput line adjoins the first water input line; and a light hydrocarboninput line coupled to the first extractive unit.
 2. The apparatus ofclaim 1, wherein the solvent stream comprises a closed-loop solventstream.
 3. The apparatus of claim 1, further comprising a solventregeneration system coupled to the solvent stream output line.
 4. Theapparatus of claim 3, wherein the solvent regeneration system comprisesa two-stage vaporization system.
 5. An apparatus for removing heavyhydrocarbons from a solvent stream, said apparatus comprising: a firstextractive unit and a second extractive unit; wherein the firstextractive unit comprises a first water input line, a solvent streamoutput line, and a first heavy hydrocarbon output line; wherein thefirst heavy hydrocarbon output line is coupled to the second extractiveunit; wherein the first water input line is supplied by condensedstripping steam; wherein the second extractive unit comprises a secondwater input line, a second water output line, and a second heavyhydrocarbon output line; and a light hydrocarbon input line coupled tothe first extractive unit.
 6. The apparatus of claim 5, wherein thesolvent stream comprises a closed-loop solvent stream.
 7. The apparatusof claim 5, further comprising a solvent regeneration system coupled tothe solvent stream output line.
 8. The apparatus of claim 7, wherein thesolvent regeneration system comprises a two-stage vaporization system.9. The apparatus of claim 5, wherein the condensed stripping steam isfrom an aromatic extractive distillation process.
 10. The apparatus ofclaim 7, wherein the condensed stripping steam is from the solventregeneration system.
 11. A method for removing heavy hydrocarbons from asolvent stream, said method comprising: a) providing a first batch of amixture comprising heavy hydrocarbons dissolved in at least one solvent;b) extracting the first batch of the mixture with a light hydrocarbonwash; c) washing the first batch of the mixture with a first water wash;wherein the light hydrocarbon wash and the first water wash produce asolvent stream depleted in heavy hydrocarbons and a heavy hydrocarbonstream dissolved in light hydrocarbons; d) removing the solvent streamdepleted in heavy hydrocarbons; e) washing the heavy hydrocarbon streamdissolved in light hydrocarbons with a second water wash; f) removingthe second water wash; and g) isolating an output stream comprisingheavy hydrocarbons dissolved in light hydrocarbons.
 12. The method ofclaim 11, wherein the solvent stream comprises a closed-loop solventstream.
 13. The method of claim 11, further comprising providing asecond batch of a mixture comprising heavy hydrocarbons dissolved in atleast one solvent and repeating steps b)-g).
 14. The method of claim 13,wherein the second water wash used to wash the first batch of themixture is subsequently transferred in a closed-loop system such thatthe second water wash comprises the first water wash for the secondbatch of the mixture.
 15. The method of claim 11, further comprisingregenerating the at least one solvent from the solvent stream depletedin heavy hydrocarbons; wherein the regenerating step comprises using asolvent regeneration system.
 16. The method of claim 15, wherein thefirst water wash comprises condensed stripping steam produced by thesolvent regeneration system.
 17. The method of claim 11, wherein athreshold concentration of the heavy hydrocarbons dissolved in the atleast one solvent triggers operation of the method.
 18. The method ofclaim 11, wherein the solvent stream comprises aromatic compounds. 19.The method of claim 11, further comprising transferring the heavyhydrocarbon stream dissolved in light hydrocarbons prior to the secondwater wash.